The man in the hat is the murderer, and the poison disappears into the bucket of the sushi restaurant. The poisoning method is as follows: first, poison the victim's paper towel while he is unprepared, and then eat sushi when the victim wipes his hands with a paper towel, which will lead to poisoning. After being poisoned, everyone will think sushi is poisonous, so he will put it on the turntable. This man put paper towels on his sushi plate in this way. At that time, the motive of the murder (I don't quite remember) was that the food comment written by the victim led to the closure of the man's sushi restaurant.